Effective relapse prevention is essential to make progress toward eliminating Driving Under the Influence of alcohol (DUI) [behavior]. Statistics from the National Highway Traffic Safety Administration reveal that almost 1/3 of those arrested for DUI are [repeat] offenders. The frequent co-occurrence of DUI [behavior] and psychiatric illness suggests that untreated psychopathology likely contributes to the persisting rate of DUI related events including [DUI-risk behaviors, offenses,] and fatalities; however, a longitudinal study of DUI relapse risk and psychiatric comorbidity has never been conducted. Before relapse prevention efforts can be improved, it is necessary to identify and account for the multiple factors that detract from or obstruct favorable treatment outcomes. Hence, the primary goal of the proposed research is to prospectively examine the impact of psychiatric comorbidity on DUI relapse [(i.e. reoffense or the recurrence of DUI-risk behaviors)] among DUI [repeat] offenders. We will advance this goal by conducting a longitudinal study of 800 DUI [repeat] offenders at the Middlesex DUlL program on the campus of Tewksbury Hospital. To establish the impact of psychiatric comorbidity on DUI relapse, participants will take part in a computer- assisted interview that employs the Composite International Diagnostic Interview (CIDI). At intake, participants will complete all CIDI modules; subsequent data collection will be restricted to selected CIDI modules and survey components specifically developed for this project to glean information pertaining to post-treatment DUI relapse. To ensure desirable participant retention rates, at intake, we will gain participants' consent to contact friends, probation officers and/or family to help locate participants. This research will effectively and economically document the relationship between the nature of existent and emergent psychiatric comorbidity and post-treatment DUI-risk behavior and reoffense. By identifying risk factors associated with relapse, this study will provide the foundation for new evidence-based treatment efforts that can curtail the rate of DUI [reoffense.]